The commander of U.S. and NATO forces in Afghanistan says neighboring Pakistan has not yet placed “adequate pressure” on the Haqqani Network of militants to prevent them from plotting deadly cross-border attacks.

Afghan authorities allege leaders of the group, which is fighting alongside the Taliban, are directing “high-profile” attacks, particularly in the capital, Kabul, from their sanctuaries on Pakistani soil, with the covert support of the country’s intelligence operatives.

“There is not adequate pressure being put on the Haqqanis" by the Pakistan government, General John Nicholson told a news conference at the Pentagon on Friday.

“The Haqqanis operationally have been able to continue to conduct operations inside Afghanistan. They constitute the primary threat to Americans, to coalition members and to Afghans, especially in and around Kabul,” he added.

Though he acknowledged the number of attacks in the capital city has fallen to 16 this year compared to 23 during the same period in 2015, crediting joint U.S. and Afghan security measures.

Pakistani authorities deny the presence of any sanctuaries and insist counter-terrorism military operations have indiscriminately targeted and uprooted all militant infrastructures on their side of the border, including those of Afghan insurgents.

FILE - Army Lt. Gen. John Nicholson testifies on Capitol Hill in Washington, Jan. 28, 2016, before the the Senate Armed Services Committee.

Relations between Islamabad and Washington have been frayed over the past decade because of U.S. frustrations over Pakistan’s alleged unwillingness to act against Haqqanis.

Last month, the U.S. administration decided not to pay the Pakistan government $300 million in military reimbursements after Secretary of Defense Ash Carter told Congress he was unable to certify the country was taking sufficient action against Haqqanis and other militant groups on its soil.

Ghani in tough spot

In his Friday briefing, Gen. Nicholson also confirmed a brother of Sirajuddin Haqqani, the chief commander of the network, is in Afghan custody and has been sentenced to death by a local court.

Afghan President Ashraf Ghani is under increasing pressure at home to ensure an early execution of the convict, Anas Haqqani, to deter his brother’s group from inflicting further bloodshed on Afghans.

But Nicholson indicated it may take a while before the high-profile trial is concluded, saying the death sentence is currently going through the appeals process.

“The trial and the subsequent appeal process is entirely in control of the Afghan government so that is up to them how this plays out… And the appeals process just began, so I would expect this to continue into 2017 because of the appeals process,” he said.

FILE - Anas Haqqani, a senior leader of the Haqqani network, arrested by the Afghan Intelligence Service (NDS) in Khost province is seen in this handout picture released Oct. 16, 2014.

The Taliban has warned of “disastrous consequences” if the higher Afghan courts also uphold Anas Haqqani’s death sentence.

“The war and its intensity will increase in all parts of the country. A lot of blood will be spilled and the government will be responsible for all of it,” the Islamist insurgency threatened in a recent statement released by its media wing.

The Taliban has described the man as “an ordinary student of [a] religious school,” saying he is not involved in any political or military activity, nor has there been any prize money on his head. It also alleges the U.S. military is behind Anas Haqqani’s arrest and the judicial verdict.

It is also widely believed that Taliban sources late last month intentionally released video to reporters of a Western couple it has been holding hostage since 2012 to pressure Kabul and U.S. authorities against the possible execution of the Haqqani family member.

The hostages include an American woman, Caitlan Coleman, her Canadian husband, Joshua Boyle, and their two children. In the leaked video, the couple has urged their respective governments to meet the demands of their captives to save their lives. The Taliban is said to have demanded the Afghan government halt execution of its prisoners.